Method of sealing a soldered joint between a semiconductor device and a substrate

ABSTRACT

Triazine polymers obtained by reacting (a) monocyanate; and (b) dicyanate and/or prepolymers thereof are used in forming interconnection structures for bonding an integrated semiconductor device to a carrier substrate.

This is a divisional application of Ser. No. 07/304,826 filed on Sep.13, 1994, and now U.S. Pat. No. 5,468,790, which is a divisional of Ser.No. 07/997,964 filed on Dec. 29, 1992, and now abandoned.

TECHNICAL FIELD

The present invention is concerned with compositions that are useful ininterconnection structures for joining an integrated semiconductordevice to a carrier substrate of organic or ceramic nature andparticularly to compositions that prior to curing are of low viscosity.The present invention is especially concerned with so-called "controlledcollapse chip connection" or "C4" that employs solder-bumpinterconnections. Such is also referred to as the face down or flip-chipbounding. The present invention is also concerned with a method ofmaking the interconnection structure.

BACKGROUND ART

Controlled collapse chip connection (C4) or flip-chip technology hasbeen successfully used for over twenty years for interconnecting highI/O (input/output) count and area array solder bumps on the siliconchips to the base ceramic chip carriers, for example alumina carriers.The solder bump, typically a 95 Pb/5 Sn alloy, provides the means ofchip attachment to the ceramic chip carrier for subsequent usage andtesting. For example, see U.S. Pat. Nos. 3,401,126 and 3,429,040 toMiller and assigned to the assignee of the present application, for afurther discussion of the controlled collapse chip connection (C4)technique of face down bonding of semiconductor chips to a carrier.Typically, a malleable pad of metallic solder is formed on thesemiconductor device contact site and solder joinable sites are formedon the chip carrier.

The device carrier solder joinable sites are surrounded bynon-solderable barriers so that when the solder on the semiconductordevice contact sites melts, surface tension of the molten solderprevents collapse of the joints and thus holds the semiconductor devicesuspended above the carrier. With the development of the integratedcircuit semiconductor device technology, the size of individual activeand passive elements have become very small, and the number of elementsin the device has increased dramatically. This results in significantlylarger device sizes with larger number of I/O terminals. This trend willcontinue and will place increasingly higher demands on device formingtechnology. An advantage of solder joining a device to a substrate isthat the I/O terminals can be distributed over substantially the entiretop surface of the semiconductor device. This allows an efficient use ofthe entire surface, which is more commonly known as area bonding.

Usually the integrated circuit semiconductor devices are mounted onsupporting substrates made of materials with coefficients of expansionthat differ from the coefficient of expansion of the material of thesemiconductor device, i.e. silicon. Normally the device is formed ofmonocrystalline silicon with a coefficient of expansion of 2.6×10⁻⁶ per°C. and the substrate is formed of a ceramic material, typically aluminawith a coefficient of expansion of 6.8×10⁻⁶ per °C. In operation, theactive and passive elements of the integrated semiconductor deviceinevitably generate heat resulting in temperature fluctuations in boththe devices and the supporting substrate since the heat is conductedthrough the solder bonds. The devices and the substrate thus expand andcontract in different amount with temperature fluctuations, due to thedifferent coefficients of expansion. This imposes stresses on therelatively rigid solder terminals.

The stress on the solder bonds during operation is directly proportionalto (1) the magnitude of the temperature fluctuations, (2) the distanceof an individual bond from the neutral or central point (DNP), and (3)the difference in the coefficients of expansion of the material of thesemiconductor device and the substrate, and inversely proportional tothe height of the solder bond, that is the spacing between the deviceand the support substrate. The seriousness of the situation is furthercompounded by the fact that as the solder terminals become smaller indiameter in order to accommodate the need for greater density, theoverall height decreases.

The disclosure of an improved solder interconnection structure withincreased fatigue life can be found in U.S. Pat. No. 4,604,644 toBeckham, et al. and assigned to the assignee of the present application,disclosure of which is incorporated herein by reference. In particular,U.S. Pat. No. 4,604,644 discloses a structure for electrically joining asemiconductor device to a support substrate that has a plurality ofsolder connections where each solder connection is joined to a solderwettable pad on the device and a corresponding solder wettable pad onthe support substrate, dielectric organic material disposed between theperipheral area of the device and the facing area of the substrate,which material surrounds at least one outer row and column of solderconnections but leaves the solder connections in the central area of thedevice free of dielectric organic material.

The preferred material disclosed in U.S. Pat. No. 4,604,644 is obtainedfrom a polyimide resin available commercially and sold under thetrademark AI-10 by Amoco Corporation. AI-10 is formed by reacting adiamine such as p,p' diaminodiphenylmethane with a trimellitic anhydrideor acylchloride of trimellitic anhydride. The polymer is further reactedwith γ-amino propyl triethoxy silane (A-1100) or β-(3,4-epoxycyclohexyl) ethyltrimethoxy silane (A-186) from Dow Corning. The coatingmaterial is described in IBM Technical Disclosure Bulletin, September1970, p. 825.

The dielectric material is typically applied by first mixing it with asuitable solvent and then dispensing it along the periphery of thedevice where it can be drawn in between the device and substrate bycapillary action.

Encapsulants that exhibit, among other things, improved fatigue life ofC4 solder connections are disclosed in U.S. Pat. No. 4,999,699 toChristie et al. and assigned to the assignee of the present invention,disclosure of which is incorporated herein by reference. In particular,U.S. Pat. No. 4,999,699 discloses a curable composition containing abinder which is a cycloaliphatic polyepoxide and/or a cyanate ester orprepolymer thereof and a filler. The cycloaliphatic polyepoxide, cyanateester and cyanate ester prepolymer employed have viscosities at normalroom temperatures (25° C.) of no greater than about 1,000 centipoise.The filler has a maximum particle size of 31 microns and issubstantially free of alpha particle emissions. The amount of binder(i.e. --epoxy and/or cyanate ester) is about 60 to about 25 percent byweight of the total of the binder and filler and, correspondingly, thefiller is about 40 to about 75 percent by weight of the total of thebinder and filler.

In addition, U.S. Pat. No. 5,121,190 to Hsiao et al. and assigned to theassignee of the present application, disclosure of which is incorporatedherein by reference, discloses providing C4 solder connections of anintegrated semiconductor device on an organic substrate. Thecompositions disclosed therein are curable compositions containing athermosetting binder and filler. The binder employed has viscosity atnormal room temperatures (25° C.) of no greater than about 1,000centipoise. Suitable binders disclosed therein include polyepoxides,cyanate esters and prepolymers thereof.

The technique disclosed therein enables chips to be attached directly onthe surface of a board thereby eliminating an intermediate chip carrier.

Although the above techniques discussed in U.S. Pat. Nos. 4,999,699 and5,121,190 have been quite successful, there still remains room forimprovement, especially with respect to relatively low temperatureprocessability.

SUMMARY OF INVENTION

The present invention is concerned with compositions that are curable atrelatively low temperatures (about 200° C. or less) and exhibitexcellent thermal stability along with relatively low coefficients ofthermal expansion. The compositions of the present invention areespecially useful in achieving fatigue life enhancement of the C4 solderconnections of an integrated semiconductor device on a substrate.

The present invention provides a composition that exhibits excellentwetting and coverage of the C4 connections as well as the pin headsunder the device that are present. In fact, the present invention makesit possible to achieve complete coverage beneath the chip. Thecompositions of the present invention prior to curing are of relativelylow viscosity and thereby exhibit even and adequate flow under thesemiconductor device.

The compositions of the present invention include a triazine polymerthat is a reaction product of (a) monocyanate; and (b) dicyanate and/ora prepolymer thereof.

The present invention is also concerned with solder interconnection forforming connections between an integrated semiconductor device and acarrier substrate. The solder interconnection includes a plurality ofsolder connections that extend from the carrier substrate to electrodeson the semiconductor device to form a gap between the carrier substrateand the semiconductor device. The gap is filled with a compositionobtained from curing the above disclosed composition.

Furthermore, the present invention is concerned with a method of sealingsoldered interconnections between a semiconductor device and asupporting substrate. The method includes attaching the device to thesubstrate by a plurality of solder connections that extend from thesupporting substrate to electrodes on the semiconductor device to form agap between the supporting substrate and the semiconductor device. Theabove disclosed composition is injected into the gap and the monocyanateand dicyanate and/or prepolymer thereof are cured to form a triazine.

SUMMARY OF DRAWINGS

FIG. 1 is a schematic diagram of a solder interconnection pursuant tothe present invention.

FIG. 2 illustrates glass transition temperature (Tg) of the cyanateblends pursuant to the present invention.

BEST AND VARIOUS MODES FOR CARRYING OUT THE INVENTION

To facilitate an understanding of the present invention, reference ismade to FIG. 1. In FIG. 1, numeral 1 represents a semiconductor chipjoined on the chip carrier 2 by solder bumps 3 mated to pads 4. I/O pins5 extend and protrude from the carrier 2, with a small portion 6 of thepins protruding from the other side of the carrier for carrying currentthereto. When the carrier is an organic substrate, the pins (6) as suchare not required. Instead, electrically conductive circuitry andinterconnections would be provided such as at the periphery of substratefor connection to a desired structure. The sealant or encapsulant 7pursuant to the present invention provides for essentially void freeencapsulation of the solder connections thereby assuring highly reliabledevices and fills the gap forming a uniform fillet around the chip aswell as covering the pin heads under the device (not shown).

The triazine polymers of the present invention that are suitable forproviding the sealant are reaction products of (a) monocyanate; and (b)dicyanate and/or prepolymers thereof.

The monocyanate is a monomeric monofunctional cyanate and includemonocyanates represented by the following formula:

    NCO--B

wherein B represents an alkyl group; alkyl substituted phenyl ring; or amoiety of the formula: ##STR1## wherein A represents a single bond,##STR2## --O--, --C(CF₃)₂, divalent alkylene radicals such as --CH₂ --and --C(CH₃)₂ --; divalent alkylene radicals interrupted by heteroatomsin the chain such as O, S and N. Each R is independently selected fromthe group of hydrogen, and alkyl containing 1 to 9 carbon atoms. Each nis independently an integer of 0 to 5.

Suitable alkyl groups for B and for substitution on a phenyl ringtypically contain 1 to 16 carbon atoms, and preferably 1 to 9 carbonatoms.

Examples of suitable monocyanates are nonylphenyl cyanate; dinonylphenyl cyanate, cumyl phenyl cyanate; phenyl cyanate, 2-,3-, or4-methyl-, ethyl-, n-propyl-, isopropyl-, n-butyl-, isobutyl-,tert-butyl-, n- or iso-pentyl-, n or isohexyl-, n- or isoheptyl-, n-orisooctyl-, n- or isononyl-, n- or isodecyl-, ethene-, propene-, butene-and ethinphenylcyanate, 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, 3,5-dimethyl-,diethyl-, dipropylphenylcyanates; 2,3,4-, 2,3,5-, 2,3,6-, 3,4,5-,2,4,6-trimethyl-, triethyl- and tripropylphenylcyanates; 2,3,4,6-,2,3,4,5-, 2,3,5,6-tetramethyl-, tetraethyl- andtetrapropylphenylcyanates and 2,3,4,5,6- penta methylphenyl cyanates.The above mentioned alkyl radicals also can be mixed, e.g. 2,6-dimethyl4-tertbutyl phenyl cyanate.

Other monocyanates include cycloalkylphenyl cyanates, for instance 2-,3- or 4- cyclohexylphenylcyanate, substituted alkylphenyl cyanates, forinstance 4-chloromethyl-, 4-hydroxy methyl-, and 3-trifluoromethylphenylcyanate; aralkylphenylcyanates, for instance 2-, 3- or 4-phenylcyanates,halogenophenyl cyanates, for instance 2-, 3-, or 4-chloro- orbromophenylcyanate, 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, 3,5-dichloro(bromo)-phenyl cyanate, 2-methyl-5-chloro-, 2-methyl-6-chloro-,3-methyl-4-chloro-, 5-methyl-2-chloro-, 2-methyl-4-chloro-, 2methyl-3-chlorophenylcyanate, nitrophenyl cyanates, alkyloxy, aryloxy-,acyloxy phenylcyanates, phenycyanates with S-containing substituents,for instance 2-, 3- or 4-methyl mercapto-ethylmercapto-, propylmercapto,phenymercapto-, acetylmercapto-, benzoylmercaptophenyl cyanates, 3- or4-rhodanophenylcyanates, 2,4-bismethyl-mercapto-3-methylphenylcyanate,cyanates from carboxylic aromatic esters other than phenyl; α- orβ-naphthylcyanates, cyanates from heterocyclic systems, for instance 3-,5-, 6-, 7- or 8-cyanatoquinoline 1-, 2-, 3- or 4-cyanatocarbazol,-carboxylic acid, 5-cyanato-1-phenyl-3-methylpyrazole, 4-, 5-, 6-, or7-cyanatobenztriazol, -benzthiazol, -benzimidazol -benzpyrazole.

The monocyanates can be prepared from the corresponding phenol analogsby reacting with a cyanogen halide such as cyanogen bromide in thepresence of base catalyst such as triethylamine.

The dicyanate esters are curable through cyclotrimerization and can bemonomeric or less desirably prepolymers, including oligomers and can berepresented by those materials containing the following formula:##STR3## wherein A represents independently a single bond, ##STR4##--SO₂ --, --O--, --C(CF₃)₂ --, divalent alkylene radicals such as --CH₂-- and --C(CH₃)₂ --; divalent alkylene radicals interrupted byheteroatoms in the chain such as O, S and N.

Each R is independently selected from the group of hydrogen, alkylcontaining 1 to 9 carbon atoms:

Each n independently is an integer of 0 to 4. Other polyfunctionalcyanates are prepared by well known methods, for example, by reactingthe corresponding polyvalent phenol with a halogenated cyanate asexemplified in U.S. Pat. Nos. 3,553,244, 3,740,348 and 3,755,402.

Examples of the polyfunctional cyanate ester include 1,3- or1,4-dicyanatobenzene; 1,3,5-tricyanatobenzene; 1,3-, 1,4-, 1,6-, 1,8-,2,6-, or 2,7-dicyanatonaphthalene; 1,3,6-tricyanatonaphthalene;4,4'-dicyanatonaphthalene; bis(4-cyanatophenyl) propane,2,2-bis(3,5-dichloro-4-cyanatophenyl)propane; bis(4-cyanatophenyl)ether; bis(4-cyanatophenyl)thioethers, bis(4-cyanatophenyl) sulfone;tris-(4-cyanatophenyl) phosphite; tris(4-cyanatophenyl) phosphate;bis(3-chloro-4-cyanatophenyl) methane; cyanated novolak derived fromnovolak, cyanated bisphenol type polycarbonate oligomer derived frombisphenol type polycarbonate oligomer, and mixture thereof. Othercyanate esters employed in the practice of this invention are listed inthe U.S. Pat. Nos. 3,553,244; 3,740,348; 3,755,402; 3,562,214; BritishPatent No. 1,060,933; Japanese patent publication (Kohkoku) Nos.18468/1968; British Patent Nos. 1,218,447 and 1,246,747 and U.S. Pat.No. 3,994,949 and Japanese Patent Publication (Kohkai) No. 26853/1972which are incorporated herein for reference.

Also, specific cyanate esters that can be employed in the presentinvention are available and well-known and include those discussed inU.S. Pat. Nos. 4,195,132; 3,681,292; 4,740,584; 4,745,215; 4,477,629;and 4,546,131; European patent application EP0147548/82; and GermanOffen. 2,611,796, disclosures of which are incorporated herein byreference.

An example of a suitable polyaromatic cyanate ester containingcycloaliphatic bridging group between aromatic rings is available fromDow Chemical Company under the designation "Dow XU-71787 cyanate. Adiscussion of such can be found in Bogan, et al., "Unique PolyaromaticCyanate Ester for Low Dielectric Printer Circuit Boards", Sampe Journal,Vol. 24, No. 6, November/December 1988. A specific polyfunctionalcyanate ester is Bisphenol AD dicyanate (d,d'-ethylidene bisphenoldicyanate) available from Ciba-Geigy under the trade designation AROCYL-10.

When prepolymers of the dicyanate are employed such typically haveconversions of up to about 30% and more typically of up to about 15%.

The amount of the monocyanate is typically about 5 to about 50%, andpreferably about 5 to about 40% and most preferably about 5 to about 30%by weight of the total of the monocyanate and dicyanate and/orprepolymer thereof.

The amount of the dicyanate and/or prepolymer thereof is correspondinglyabout 50 to about 95% by weight, preferably about 60 to about 95% byweight, and most preferably about 95 to about 70% by weight of the totalof the monocyanate and dicyanate and/or prepolymers thereof.

Compositions of the present invention can also include a filler andespecially an inorganic filler. The particular size of the filler istypically not greater than about 49 microns or less, preferably about0.7 to about 40 microns. This is desirable so that the compositions willhave the desired CTE and viscosity characteristics and readily flow inthe gap between the chip and substrate carrier. The gap is normallyabout 25 to about 160 microns and preferably about 75 to about 125microns. The preferred fillers have average particle size of about 5 toabout 25 microns.

In addition, the filler should be at least substantially free of alphaparticular emissions such as from the trace amounts of radioactiveimpurities such as uranium and thorium normally present in conventionalsilica or quartz fillers. The fillers employed have emission rates ofless than 0.01 alpha particles/cm² -hr and preferably less 0.005 alphaparticles/cm² -hr. The presence of alpha particle emissions primarilycaused by the presence of uranium and thorium isotopes in the fillerscan generate electron/hole pairs which in turn would be detrimental tothe device. The preferred filler is high purity fused or amorphoussilica. A commercially available filler that can be employed is DP4910from PQ Corporation. The preferred filler can be optionally treated witha coupling agent.

The compositions of the present invention contains about 30 to about 50%by weight and preferably about 40% by weight of the binder andcorrespondingly about 70% to about 50% by weight and preferably about55% by weight of the filler. These amounts are based upon the totalamounts of binder and filler in the composition.

In addition to the binder and filler, the compositions can also includea catalyst to promote the polymerization of the cyanate ester mixture.Suitable catalysts for the cyanate ester include Lewis acids, such asaluminum chloride, boron trifluoride, ferric chloride, titaniumchloride, and zinc chloride; salts of weak acids, such as sodiumacetate, sodium cyanide, sodium cyanate, potassium thiocyanate, sodiumbicarbonate, and sodium boronate. Preferred catalysts are metalcarboxylates and metal chelates, such as cobalt, iron, zinc, manganeseand copper acetylacetonate or octoates or naphthenates. The amount ofcatalyst when used can vary, and generally will be 0.005 to 5 weightpercent, preferably 0.05 to 0.5 weight percent based on total solidbinder weight.

Surfactants in amounts of about 0.5% to about 3% and preferably about 1%to about 1.4% can be used to facilitate flow of the compositions.Suitable surfactants include silanes and non-ionic type surface activeagents.

Especially preferred are the non-ionic alkylphenyl polyether alcoholsincluding those available under the trade designation Triton from Rohm &Haas Co. These surface active agents are prepared by the reaction ofoctylphenol or nonylphenol with ethylene oxide and have the followinggeneral structural formula, respectively: ##STR5## in which the alkylgroup is a mixture of branched-chain isomers and x is the average numberof ethylene oxide units in the ether side chain. Products of the aboveseries of compounds include:

    ______________________________________                                        Octylphenol Series                                                            Triton        x-15          x = 1                                             Triton        x-35          x = 3                                             Triton        x-45          x = 5                                             Triton        x-114         x = 7-8                                           Triton        x-100         x = 9-10                                          Triton        x-102         x = 12-13                                         Triton        x-165         x = 16                                            Triton        x-305         x = 30                                            Triton        x-405         x = 40                                            Triton        x-705-50%     x = 70                                            Triton        x-705-100%    x = 70                                            Nonylphenol Series                                                            Triton        n-17          x = 1.5                                           Triton        n-42          x = 4                                             Triton        n-57          x = 5                                             Triton        n-60          x = 6                                             Triton        n-87          x = 8.5                                           Triton        n-101         x = 9-10                                          Triton        n-111         x = 11                                            Triton        n-150         x = 15                                            Triton        n-101         x = 40                                            ______________________________________                                    

The preferred compositions of the present invention also include anorganic dye in amounts less than about 0.2% to provide contrast.Suitable dyes are nigrosine and Orasol blue GN.

The preferred compositions of the present invention are substantiallyfree (e.g.--less than 0.2% by weight) if not completely free fromnon-reactive organic solvents.

Compositions employed pursuant to the present invention have viscosityat 25° C. (Brookfield cone & plate Spindle 51, 20 RPM or equivalent) ofabout 2,000 to about 30,000 centipoise and preferably about 2,000 toabout 20,000 centipoise. The compositions can be cured at temperaturesof about 180° C. to about 200° C. in about 1 to about 2 hours andpreferably about 1.5 hours. The compositions when cured have alphaparticle emissions of less than about 0.005 preferably less than about0.004 counts/cm2-hr and most preferably less than about 0.002 counts/cm²-hr. The cured compositions also have coefficient of thermal expansionof about 24 ppm/°C. to about 38 ppm/°C., glass transition temperature ofgreater than about 125° C. and preferably about 140° C. to about 200° C.The cured compositions have Shore D hardness of greater than 90, modulusof elasticity at 25° C. of greater than 1.0 Mpsi and preferably greaterthan 1.2 Mpsi.

The compositions are prepared by rapidly admixing the components undervacuum usually about 5 mm Hg either using a double planetary mixer orhigh shear mixer under vacuum to provide better and homogenouscompositions.

The composition is applied by dispensing through nozzles under pressureof about 20 to about 50 psi and temperatures of about 40° C. to about80° C. The compositions completely cover the C4 connections and pinheads.

It is preferred that the substrates be at a temperature of about 65° C.to about 100° C. during the dispensing.

The compositions are then cured by heating to about 150° C. to about200° C. for about 1 hour to about 3 hours and preferably about 1.5 hoursto about 2.0 hours. The substrate employed can be an organic, inorganicor composite in nature. The preferred substrate can be a ceramic moduleor a multilayer printed circuit board. The preferred ceramic substratesinclude silicon oxides and silicates such as aluminum silicate, andaluminum oxides.

The organic substrates can be thermoplastic as well as thermosettingpolymeric materials.

The preferred printed circuit board includes conventional FR-4 epoxy andlaminates based on high temperature resins such as high temperatureepoxies, polyimides, cyanates (trizines), fluoropolymers,benzocyclobutenes, polyphenylenesulfide, polysulfones, polyetherimides,polyetherketones, polyphenyquinoxalines, polybenzoxazoles, andpolyphenyl benzobisthiazoles.

The polymers can be reinforced such as with glass, for instanceepoxy-glass substrates. Also the substrates can be rigid or flexible.Suitable flexible substrates include the flexible polyimide substrates.

The following non-limiting examples are presented to further illustratethe present invention.

EXAMPLE 1 Preparation of Dinonyl Phenol Cyanate (DNPC)

Dinonyl phenol-flashed is obtained from Texaco Chemical Company. It is aviscous liquid possessing a slight phenolic odor and is a mixture ofdinonyl phenols, predominantly ortho-para-substituted. The nonyl groupsare randomly branched. It is used in the synthesis of the cyanate esterwith no further purification.

Distilled water (about 30 ml) and bromine (about 22 g) are introducedinto a 500 ml three necked round-bottom flask equipped with a lowtemperature thermometer, mechanical stirrer, and a 100 ml pressureequalizing dropping funnel. The mixture is stirred rapidly and cooled to-5° C. in an ice-salt bath. Sodium cyanide (about 6.5 g) in water (about30 ml) is then added drop-wise over a period of 30 min; the temperatureis maintained below about 5° C. during the addition. The solutiongradually turns bright yellow. After 15 min, dinonyl phenol, about 44.6g in carbon tetrachloride (about 100 ml) is added all at once withvigorous stirring. Triethylamine (about 15 g) is then added over aperiod of about 30 min; the temperature is maintained below about 10° C.during the addition. The mixture is stirred for an additional 15 min.The organic layer is then separated, washed with water (2×100 ml), dried(Na₂ SO₄), and concentrated. The resulting syrupy material is loaded ona short column of silica gel (about 150 g, in a sintered glass funnel)and the product eluted with hexane. The filtrate is concentrated toafford about 26 g (54%) of dinonyl phenol cyanate as a light yellowliquid. Positive identification is made by the absorption peak at 2266cm⁻¹, which is characteristic of the OCN vibration.

EXAMPLE 2

Nonyl phenyl cyanate and p-cumyl phenyl cyanate are prepared from thecorresponding phenol analogs according to the procedure described inexample 1.

EXAMPLE 3

The Arocy L-10 monomer is obtained from Ciba Geigy as a liquid with apurity greater than 99.95%. Blends of Arocy L-10, containing up to 40percent monocyanate i.e. (dinonyl (dinonyl phenol cyanate, nonyl phenylor p-cumyl phenyl cyanate) are dissolved by simply mixing the twomonomers in the appropriate amounts. The resulting mixtures arecatalyzed with zinc octoate (100 ppm zinc metal). Zinc octoate isobtained from Mooney Chemicals, Cleveland, Ohio 44113 as an 8% (zincmetal) solution in mineral spirits.

The glass transition temperature of each blend is determined using aDuPont 912 dual sample DSC, coupled to the 9900 Thermal Analyzer. Theinstrument is purged with nitrogen at a flow rate of less than 50 cc/minduring each run. The sample size is approximately 8 mg and the heatingrate is about 20° C./minute. Results are graphically presented in FIG.2.

EXAMPLE 4

A composition containing about 80 parts by weight of bisphenol ADdicyanate available from Ciba-Giegy as Arocy L10, about 20 parts ofdinonyl phenyl cyanate; about 145 parts by weight of fused silica(DP4910 from PQ Corporation) and having a particle size of 49 micronsmaximum and being free of alpha particle emissions; about 3 parts byweight of Triton X-100; about 0.1 parts by weight of the zinc octanoate(8% zinc in mineral spirits); and about 0.1 parts by weight of nigrosineis prepared.

The composition is dispensed at a temperature of about 50° C. in the gapof about 5 mils between a silicon chip soldered by solder bumps to 28 mmby 28 mm Al₂ O₃ substrate having pins protruding therefrom. Thecomposition is cured at about 180° C. in about 2 hours. The compositionhas a coefficient of thermal expansion of less than 28×10⁻⁶ /°C.

The structures tested for fatigue life exhibit no failures uponthermocycling the test vehicles for over 5,000 cycles between 0° C. to100° C. On the other hand, control test vehicles filled with prior artcompositions show failures at about 2,000 cycles.

EXAMPLE 5

A liquid mixture containing about 67 parts by weight of bisphenol ADdicyanate available from Ciba-Giegy as Arocy L10; about 33 parts byweight of p-cumyl phenyl cyanate (from example 2); about 148 parts byweight of fused silica available under the trade name DP4910 from PQCorporation; about 3 parts by weight of Triton X-100 (a non-ionicsurfactant); about 0.1 parts by weight of manganese naphthenate andabout 0.1 parts by weight of orasol Blue GN is prepared.

The composition is dispensed at a temperature of about 30° C. in the gapof about 5 mils between a silicon chip soldered by solder bumps to anFR-4 epoxy-glass substrate. The mixture covers the solder bumps andforms a fillet around the device. The composition is cured at about 170°C. in about 2 hours. The composition has a coefficient of thermalexpansion of less than 30×10⁻⁶ /°C.

EXAMPLE 6

A liquid mixture containing about 70 parts by weight of bisphenol ADdicyanate available from Ciba-Giegy as Arocy L10; about 30 parts byweight of nonyl phenyl cyanate (from example 2); about 150 parts byweight of fused silica available under the trade name DP4910 from PQCorporation; about 2.5 parts by weight of Triton X-100; about 0.2 partsby weight of zinc octanoate and about 0.3 parts by weight of nigrosineis prepared.

The composition is dispensed at a temperature of about 60° C. in the gapof about 5 mils between a silicon device flip-chip bonded to a high Tqepoxy-glass substrate. The composition is cured at 170° C. in about 2hours and forms a fillet around the silicon chip, on all four sides. Thecomposition has a coefficient of thermal expansion of less than 28×10⁻⁶/°C.

What is claimed:
 1. A method of sealing a soldered joint between asemiconductor device and a substrate comprising the steps of:a)injecting a thermosetting composition containing as binder (1) amonomeric dicyanate and (2) a monomeric monocyanate into a gap locatedbetween the integrated circuit chip and the substrate, wherein theamount of (2) is about 5 to about 50% by weight of the total of (1) and(2), and correspondingly, the amount of (1) is about 50% to about 95% byweight based upon the amount of (1) and (2); and wherein saidcomposition further comprises filler having a maximum particle size ofabout 49 microns and being substantially free of alpha particleemissions; wherein the amount of the binder is about 30% to about 50% byweight of the total of binder and filler and correspondingly, the amountof filler is about 50% to about 70% by weight based upon the weight ofpolymer and filler; and b) curing the dicyanate and monocyanate to forma triazine.
 2. The method of claim 1 wherein said monocyanate isselected from the group consisting of nonylphenyl cyanate; dinonylphenyl cyanate, cumyl phenyl cyanate and mixtures thereof.
 3. The methodof claim 2 wherein said dicyanate is 4,4'-ethylidene bisphenoldicyanate.
 4. The method of claim 1 wherein said composition furthercontains about 0.5% to about 3% by weight of a surfactant.
 5. The methodof claim 4 wherein said composition further includes a catalyst.
 6. Themethod of claim 1 wherein said gap is about 2 to about 6.0 mils wide. 7.The method of claim 1 wherein said composition exhibits a viscosity of25° C. (Brookfield cone and plate spindle 51, 20 RPM or equivalent) ofabout 2000 to about 3000 centipoise and that is curable at about 200° C.or less.
 8. The method of claim 1 wherein said composition furtherincludes about 1% to about 1.4% by weight of a surfactant.
 9. The methodof claim 1 wherein the amount of filler is about 55% by weight.
 10. Themethod of claim 1 wherein said composition has a viscosity at 25° C. isabout 2000 to about 20,000 centipoise.
 11. The method of claim 1 whereinsaid filler is an inorganic filler selected from the group of silica,quartz and fused silica coated with coupling agents.
 12. The method ofclaim 1 wherein said filler has emission rate of less than 0.005 alphaparticles/cm² -hr.
 13. The method of claim 1 wherein said filler hasparticle sizes of about 0.5 to about 49 micrometers.
 14. The method ofclaim 1 wherein said composition is free of unreactive organic solvents.15. The method of claim 1 wherein said composition further includes acatalyst.
 16. The method of claim 4 wherein said surfactant is selectedfrom the group consisting of silanes and non-ionic surface activeagents.
 17. The method of claim 4 wherein said surfactant is a non-ionicalkylphenyl polyether alcohol.
 18. The method of claim 1 wherein saidsubstrate carrier is a ceramic.
 19. The method of claim 1 wherein saidsubstrate carrier is an FR-4 epoxy.
 20. The method of claim 1 whereinsaid substrate carrier is an epoxy-glass reinforced substrate.
 21. Themethod of claim 1 wherein said substrate is a polyimide flexiblesubstrate.
 22. The method of claim 1 wherein said substrate is athermoplastic substrate.